1. Field of the Invention
The present invention generally relates to dual-mode transceivers capable of operating in the Code Division Multiple Access (CDMA) or Time Division Multiple Access (TDMA) mode. More particularly, the present invention is directed to CDMA/TDMA transceivers in which CDMA/TDMA filter units, such as chip matched filters, multi-code RAKE receivers or finite impulse response (FIR) filters, are configured using tri-code correlators for CDMA/TDMA related applications.
2. Description of the Related Art
The Global System for Mobile Communication (GSM) system is currently the most widely used cellular standard in the world for supporting voice and short message services. The GSM system is one type of TDMA capable of providing pack-switched high speed data services and high-speed data transmission through General Packet Radio Service (GPRS). However, due to the harmonization of third generation cellular standards/modes (i.e., broadband mobile communications with voice, video, graphics, audio and other information), the GSM/TDMA system will eventually converge with the CDMA system. During this evolution period from the second generation cellular standards/modes to the third generation cellular standards/modes, it is important to develop a suitable CDMA/TDMA dual-mode transceiver that can operate in either CDMA or TDMA mode so that the TDMA and CDMA standards/modes can coexist.
Conventional dual mode receivers or correlators usually use dedicated hardware for each of the two modes, respectively. Even though it is possible that software radios can be used to accommodate TDMA and CDMA standards/modes because software radios migrate the traditional hard-wired radio platforms to flexible software radio platforms for supporting multiple modulation waveforms and multiple air interface standards, currently there is no design for a CDMA/TDMA type of dual-mode transceiver.
One object of the present invention is to propose a tri-code correlator, which can correlator the input with code 1, xe2x88x921, or 0 instead of 1 and xe2x88x921 in order to support multi-code de-spreading or FIR filtering functionality.
It is another object of the present invention to employ tri-code correlators in configuring a chip matched filter or multi-code RAKE receiver for use by a CDMA/TDMA dual-mode transceiver in CDMA related applications, such as chip-rate de-spreading, code acquisition, code tracking, and RAKE combining.
It is a further object of the present invention to employ tri-code correlators in configuring an FIR filter for use by a CDMA/TDMA dual-mode transceiver in TDMA related applications, such as shaping/matched filter or symbol synchronization.
In accordance with the present invention, one or more tri-code correlators can be configured, in terms of software radio systems, as a generic module for use by the CDMA/TDMA dual mode transceiver.
A constructed correlator filter in accordance with the present invention includes a controller for calculating I and Q symbols and dual-code correlator banks connected to the controller for receiving input and correlating I and Q codes. In particular, each dual-code correlator bank is consisted of an array of dual-code correlators (i.e., a pair of tri-code correlators having a common input).
A constructed FIR filter in accordance with the present invention includes a controller for calculating I and Q symbols and dual-code correlator banks connected to the controller for receiving data and processing FIR coefficients in a canonical signed digit (CSD) format. In particular, each dual-code correlator bank is consisted of an array of dual-code correlators (i.e., a pair of tri-code correlators with a common input).